Fragmented RemoteFX & NSCodec Encoding, Core Server-Side Fixes, WinPR Utilities Expansion

Added new fragmented RemoteFX & NSCodec encoders that take a maximum output size and return an array of messages which can then be written to a stream. This enables proper packaging of updates that won't violate the maximum fast path pdu size. The internals of the encoders has been significantly reworked, but the previous unfragmented API remains untouched.

Fix some issues with server-side core messages like bitmap update sending.

Fix Mac OS X 32-bit, Universal and out of source builds.

Implement asynchronous mode for the ListDictionary

Add support for buffers of a variable size in the BufferPool (used for NSCodec, while RemoteFX uses fixed-size)